Investment Securities (Securities With Unrealized Losses And Length Of Impairment Period) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Investment [Line Items]
Less than 12 months, Fair Value	$ 4,352,838	$ 2,125,723
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	31,844	5,488
12 months or longer, Fair Value	767,349	1,137,135
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	20,776	29,896
Total, Fair Value	5,120,187	3,262,858
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	52,620	35,384
US Treasury and Government [Member]
Investment [Line Items]
Less than 12 months, Fair Value	491,998	90,261
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	3,098	818
12 months or longer, Fair Value	31,012	32,077
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	4,723	4,206
Total, Fair Value	523,010	122,338
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	7,821	5,024
US Government-sponsored Enterprise Debt Securities [Member]
Investment [Line Items]
Less than 12 months, Fair Value	157,830	224,808
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1,975	922
12 months or longer, Fair Value	110,250	224,779
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	2,571	7,118
Total, Fair Value	268,080	449,587
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	4,546	8,040
State and municipal obligations [Member]
Investment [Line Items]
Less than 12 months, Fair Value	66,998	172,980
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	544	646
12 months or longer, Fair Value	31,120	215,702
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1,195	7,708
Total, Fair Value	98,118	388,682
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	1,739	8,354
Agency mortgage-backed securities [Member]
Investment [Line Items]
Less than 12 months, Fair Value	530,035	55,128
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	2,989	429
12 months or longer, Fair Value	291,902	381,617
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	5,617	5,163
Total, Fair Value	821,937	436,745
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	8,606	5,592
Non-agency mortgage-backed securities [Member]
Investment [Line Items]
Less than 12 months, Fair Value	653,603	141,655
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	7,059	609
12 months or longer, Fair Value	54,536	43,659
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	760	619
Total, Fair Value	708,139	185,314
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	7,819	1,228
Asset-backed Securities [Member]
Investment [Line Items]
Less than 12 months, Fair Value	2,207,922	1,424,457
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	12,492	2,009
12 months or longer, Fair Value	223,311	159,098
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	4,615	3,094
Total, Fair Value	2,431,233	1,583,555
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	17,107	5,103
Total mortgage and asset-backed securities [Member]
Investment [Line Items]
Less than 12 months, Fair Value	3,391,560	1,621,240
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	22,540	3,047
12 months or longer, Fair Value	569,749	584,374
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	10,992	8,876
Total, Fair Value	3,961,309	2,205,614
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	33,532	11,923
Other debt securities [Member]
Investment [Line Items]
Less than 12 months, Fair Value	244,452	16,434
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	3,687	55
12 months or longer, Fair Value	25,218	80,203
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1,295	1,988
Total, Fair Value	269,670	96,637
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 4,982	$ 2,043